while loop not working Java

Question

When I create a variable and wrap the code in a while loop it never repeats. Here's a sample of code I tried it on.

String repeat = "y";
    Scanner keyboard = new Scanner(System.in);
    while (repeat == "y"){
        String word1 = "this";
        String word2 = "that";
        String word3 = word1 + word2;
        System.out.println(word3);
        for(int x = 10; x<20; x = x+1){

            word3 = word1 + word3;
            System.out.println(word3);
        }
        repeat = keyboard.nextLine();
    }

No matter what the input is in the end of the script, it just ends. Any help?

Use `String`'s `equals` method to compare `String` values, not `==`, which compares object references to determine if they refer to the same object. — rgettman, Sep 06 '13 at 17:47
@rgettman They are literals here though, unless there's something missing in the code. — Sotirios Delimanolis, Sep 06 '13 at 17:48
@SotiriosDelimanolis Yes, they are literals, so `"y"` will be interned. The `while` loop will be entered for that reason. But after `repeat = keyboard.nextLine();`, then `repeat` won't be a literal any more. Either way, `.equals` is needed here. — rgettman, Sep 06 '13 at 17:50
@rgettman Right, it'll fail the next time. I stopped thinking :) — Sotirios Delimanolis, Sep 06 '13 at 17:50

score 1 · Accepted Answer · edited May 23 '17 at 12:29

1

Change the line

 while (repeat == "y")

to

while("y".equalsIngnoreCase(repeat))

and

keyboard.nextLine() ;

to

keyboard.next();

Reading How do I compare strings in Java? will be helpful.

edited May 23 '17 at 12:29

Community

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answered Sep 06 '13 at 17:48

Prabhaker A

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I deleted my answer because I checked the javadoc, and Scanner does not have a `readLine()` method. – Marcelo Sep 06 '13 at 17:52
1

@Marcelo Yes .it has next() method to read line .I have updated it. – Prabhaker A Sep 06 '13 at 17:53

score 0 · Answer 2 · answered Sep 06 '13 at 17:49

0

When you compare a string using '=='. you are comparing the object reference. You are essentially asking if the two objects are the same, rather than comparing the string contents. Try using the String.compareTo(..) method.

Example:

while (repeat.compareTo("y") == 0) {

answered Sep 06 '13 at 17:49

samsquanch

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Why `compareTo` over `equals`? – Cruncher Sep 06 '13 at 17:50
There is no preference, other than that you could diverge extra information from the return value, otherwise equals works as well. – samsquanch Sep 06 '13 at 17:51
If you look at the source code of `equals` and `compareTo` you will see that `equals` is definitely faster. – Marcelo Sep 06 '13 at 18:03

score 0 · Answer 3 · answered Sep 06 '13 at 17:49

0

The problem probably comes from the facts you compare two objects with = but I guess what you want to do is compare Strings with the String method equals, so it would look like that:

while(repeat.equals("y")){
...
}

answered Sep 06 '13 at 17:49

Barbe Rouge

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score 0 · Answer 4 · answered Sep 06 '13 at 17:49

0

Never use == to compare strings.

Try this:-

  while ("y".equalsIngnoreCase(repeat) )

answered Sep 06 '13 at 17:49

Rahul Tripathi

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while loop not working Java

4 Answers4